Hi. I've sort of jumped into the world of self-made electronics this past year, and I just completed my first stand alone PWM. I like to think I'm pretty good at understand and following schematics (I successfully built a constant current PWM earlier before this 555 PWM), but when it comes down to it, I still don't really understand WHAT all is going on.
As such, when it comes to trying to get this 555PWM to get any more dim, I'm at a loss.
Here's the circuit:
I'm trying to get it to dim almost completely, but with P1 turned all the way, its still bright enough to read comfortably with in a dark room. Turned all the way the other way, it's as bright as an LED at 12v with a 470Ω resistor should be.
I've tried soldering a couple of 10k resistors on one side of the pot to test and see if a larger pot (100k? 200k?) would make a difference, but it didn't really seem to make it any dimmer.
Here's my parts list for this build:
LM555CN LM555CN - Timer
BD681 BD681 NPN Power Transistor
C470U25E 470uF 25V Radial Electrolytic Capacitor
1N60P 1N60P Germanium Diode
1N4148 1N4148 100V 200mA General Purpose Diode
C0001UT 0.1uF 35V Tantalum Capacitors
C010UC 0.01uF 50V Ceramic Capacitors
POT50K 50k Linear Taper Pot
R001K14W 1.0kohm 1/4W 5% Carbon Film Resistor
I'm using the germanium diodes since it sounds like those permit a wider % of duty range.
Edit: I just realized something while doing some reading, my 0.1uF capacitor (C1) is a Tantalum capacitor which is polarized. Should I be using a non-polarized 0.1uf cap (maybe ceramic) for this, or does it not matter? I have a 104-coded ceramic cap I can pull off an old power supply board I've been savaging for parts.
I figure if I can change the frequency, I can get the perception of a dimmer light; because as I understand it, the potentiometer controls duty cycle.
I could just put a switch in-line with the LEDs, but that would be more "stuff" attached the project, and I'd really like the lights to be controlled primarily by the pot. It doesn't have to turn entirely off, but be really dim.
Any help is greatly appreciated.
Oh, these PWMs are going to be used for a couple of projects; the current (haha ... eh, sorry) projects are:
1. Converting my Datsun 280Z's dash lights to LEDs
2. An RGB LED lamp for a girl I have a crush on - I figure by using a PWM on each of the colors, she can change the color of the lamp on a whim.
3. A really slow circuit for when I change the exterior lights and taillights on the above Z to LEDs, for use as a blinker circuit. I'd like to do some neat tricks with the brake lights (like maybe some sequential illumination tricks), but I think that's beyond me at the moment.
As such, when it comes to trying to get this 555PWM to get any more dim, I'm at a loss.
Here's the circuit:
I'm trying to get it to dim almost completely, but with P1 turned all the way, its still bright enough to read comfortably with in a dark room. Turned all the way the other way, it's as bright as an LED at 12v with a 470Ω resistor should be.
I've tried soldering a couple of 10k resistors on one side of the pot to test and see if a larger pot (100k? 200k?) would make a difference, but it didn't really seem to make it any dimmer.
Here's my parts list for this build:
LM555CN LM555CN - Timer
BD681 BD681 NPN Power Transistor
C470U25E 470uF 25V Radial Electrolytic Capacitor
1N60P 1N60P Germanium Diode
1N4148 1N4148 100V 200mA General Purpose Diode
C0001UT 0.1uF 35V Tantalum Capacitors
C010UC 0.01uF 50V Ceramic Capacitors
POT50K 50k Linear Taper Pot
R001K14W 1.0kohm 1/4W 5% Carbon Film Resistor
I'm using the germanium diodes since it sounds like those permit a wider % of duty range.
Edit: I just realized something while doing some reading, my 0.1uF capacitor (C1) is a Tantalum capacitor which is polarized. Should I be using a non-polarized 0.1uf cap (maybe ceramic) for this, or does it not matter? I have a 104-coded ceramic cap I can pull off an old power supply board I've been savaging for parts.
I figure if I can change the frequency, I can get the perception of a dimmer light; because as I understand it, the potentiometer controls duty cycle.
I could just put a switch in-line with the LEDs, but that would be more "stuff" attached the project, and I'd really like the lights to be controlled primarily by the pot. It doesn't have to turn entirely off, but be really dim.
Any help is greatly appreciated.
Oh, these PWMs are going to be used for a couple of projects; the current (haha ... eh, sorry) projects are:
1. Converting my Datsun 280Z's dash lights to LEDs
2. An RGB LED lamp for a girl I have a crush on - I figure by using a PWM on each of the colors, she can change the color of the lamp on a whim.
3. A really slow circuit for when I change the exterior lights and taillights on the above Z to LEDs, for use as a blinker circuit. I'd like to do some neat tricks with the brake lights (like maybe some sequential illumination tricks), but I think that's beyond me at the moment.
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